The Problem With Oxygen Depletion Sensors…

The problem with oxygen depletion sensors is that they don’t sense oxygen.  Oxygen depletion sensors (ODS) are found on gas log appliances and are intended to shut the appliance off before the oxygen in a space falls to a dangerous level.  ODS sensors are thermocouples which produce a millivoltage when heated.  For this reason, the sensing end of an ODS sensor should be in contact with the pilot flame.  When operating properly, the flame heats the thermocouple which produces a millivoltage which in turn keeps the main gas valve open and allows gas to flow to the main burner.  When the flame cools as a result of low oxygen levels, the thermocouple or ODS fails to produce the necessary power to keep the main gas valve open and allows it to close, preventing gas flow and subsequent ignition.  The real problem however, is not low oxygen level, but the production and distribution of soot.  Anyone who has ever dealt with a soot damaged home knows how difficult the process can be to recover from the damage.  You see, appliances that burn with a yellow flame are already burning natural or propane gas incompletely.  That is, the carbon not consumed by the combustion process, will be visible and deposited as soot on clothing, furniture, draperies and appliances.   As a result, the ODS will NOT shut down the unit in time to prevent a soot production problem.  The lesson to be learned here is that even though your appliance has an ODS, don’t be fooled into thinking that you are protected.  Remember, if your appliance is designed to burn with a yellow flame, it is already producing soot.  Keep an eye on your fireplace insert, particularly if yours is unvented.  You will eventually see soot on the inside walls and if you see it there, it’s in the house!  The only way to prevent further damage is to quit using the gas logs set.


What’s Wrong With This Picture?

In a recent investigation of a crane outrigger failure, we were provided with some photographs of the incident by the insured company’s personnel.  At the time of the outrigger failure, the insured company was attempting to lift crawler tracks for attachment to a 120 ton crane using a 40 ton boom truck.  It was understood that the weight of the tracks was 26,300 pounds.  However, as soon as one track was lifted off the ground, the left rear outrigger buckled.  From all indications, the load was under the load limit capacity of the boom truck.  Upon reviewing the photos that were taken by the insured company, and specifically the area where the buckling occurred in zoom mode, it was noted that the outrigger failed at the point were it exits its storage enclosure.  Upon further inspection of the photograph, something very unusual was noted.  Can you tell what it is by looking at the picture below

Give up?  If you look to the left of the area where the outrigger buckled you will see that the rear end of the large crane is resting on a part of the bed of the boom truck.  In the original photograph provided by the insured company, the position of the large crane on the boom truck bed, is not obvious because it was taken at a distance of several feet away from both vehicles.  The question then arises as to whether the view could have been distorted because of the angle of the photographer as they took the photograph.  The answer is no.  As it turned out, the insured company also provided additional photographs which documented the position of the large crane on the bed and after it was completely removed.  Unfortunately, those photographs cannot be published because they can identify the insured company and therefore, constitute a privacy issue.  Suffice it to say that the partial load of the large crane was enough to cause the outrigger to buckle when combined with the track load of 26,300 pounds.

ATTENTION Tennessee High School Seniors and Current Engineering Students

It’s not too early to start thinking about scholarships for your college education.  R.J. Hill Consulting is continuing to offer a $500 scholarship to any Tennessee high school student interested in pursuing a career in engineering.  This scholarship is also available to any currently enrolled engineering student in a Tennessee public university.  The application instructions are available on our website.  Go to then click on “Scholarship Awards and Instructions”.  Scroll down below the scholarship announcement and you will find the instructions listed.  The deadline for application is March 31, 2018.  Although this date seems far in the future, time will pass quickly.  So, be mindful of the time needed to write the required essay.  Good Luck

Pumps and Glycol Solutions

Just completed two webinars; one on the use of glycols as heat transfer fluids and the other on retrofitting pumps in HVAC applications.  Both of these topics are related in that pumps are used to circulate fluids, including glycols, to transfer heat.  Typical applications for glycol use include the food and beverage industry, HVAC, and process chemical.  Pumps applications not only include the previously stated industries but also, utility; both electrical and water, petrochemical, and plastics, to name a few.  Insurance carriers that cover businesses in these industries need to be concerned because property damage as well as personal injury can occur when spills and pump failures occur.  Corrosion is a major problem in systems using carbon steel piping as a conduit for the transmission of the gylcol.  If not properly mixed and the correct inhibitors added, the glycol solution can be acidic and cause wear to occur in pipes and fittings resulting in leaks and spills, if not carefully monitored.  Similarly, the internal components of pumps can come under attack and fail as a result of the acidic conditions that could arise if the glycol solution is not properly mixed.  However, during such instances, insurance carriers are also considering the possibility of subrogating against a third party in order to recover their expenditures.  Potential defendants would include the company mixing and/or installing the glycol solution, the designer and installer of the piping system, and the selector and installer of the pump used in circulating the glycol.  It should be noted that the internal components of the pump can be selected based on compatibility of the fluid to be circulated.

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